The long-term goal of this project is to understand the intracellular processing of Paramyxovirus attachment glycoprotein and fusion glycoprotein. The specific aims of this application are: 1. To define the steps in membrane insertion of the HN and F glycoproteins of Newcastle disease virus focusing on the signals required for membrane insertion and the final correct membrane topology of each protein, 2. To define intracellular processing of the two proteins focusing on the requirements for proper folding of the proteins and the cellular machinery involved in this process, 3. To define the sequences required for the proper assembly of the HN protein at the cell surface and into virions. The steps in membrane insertion will be characterized in cell-free translation systems containing membranes. Events just subsequent to membrane insertion will also be examined in a cell-free system. The effect of mutations on the folding and subsequent transport of the protein through the cell will also be explored by transfecting cells with altered genes. Infected cells will also be used to characterize wild-type proteins. Lastly, a complementation system between cells transfected with an altered gene and virus defective in the expression of that gene will allow determination of the sequence requirements for proper assembly of the proteins into virions. These studies are relevant to an understanding of eucaryotic cell pathways used for the membrane insertion, transport and processing of glycoproteins in general. Principles established for these proteins will have relevance to glycoproteins in general. These studies are also important to an understanding of the structural determinants of the function of Paramyxovirus glycoproteins. A full understanding of the structural determinants of function requires an understanding of the steps necessary to acquire the proper structure.